Heretofore, threaded pipe couplings either of metals or synthetic plastic materials have required prethreading the pipe with an appropriate die tool, this being a disadvantage because a die tool is expensive and difficult to use. Another disadvantage to this type of coupling lies in the requirement that pipe caulk or similar material must be expertly employed to obtain a fluid tight seal.
Synthetic pipe couplings are also known in which an O-Ring, or a similar washer, and a gripping metal ring are factory assembled within the fitting to produce a self-supporting and fluid tight coupling. The disadvantage of this type of assembly is that the coupling cannot be disassembled.
Synthetic pipe couplings are also known in which the fitting is inserted inside the pipe. The assembly is secured by a metal ring compressed by a crimping tool.
This type of coupling has three disadvantages: first, the fitting's internal bores are smaller than the pipe interior diameter; second, the metal ring can easily corrode, and third, the crimping tool is too expensive for the occasional customer, especially in the do-it-yourself market.
Other synthetic plastic pipe couplings are also known in which the assembly is created by the concurrence of a sealing element and an incrustating metal ring, held to the fitting by a threaded nut.
This type of coupling has two disadvantages: first, they are very costly due to the multiple parts that compose the assembly, and second, they are too voluminous in relation to the pipe diameter, a notorious hindrance when employed within thin walls.
Some synthetic plastic pipes can be coupled through solvent welding. Such couplings cannot be disassembled and reused, and they cannot be repaired.
Some other synthetic plastic pipes can be fusion welded. This method required expensive tooling and great expertise, being restricted in its usage to a few specialized fields.
The invention overcomes the foregoing disadvantages of heretofore known couplings.